In a small bowl, mix premade ranch dressing and mustard. Pour 1/4 cup of mixture onto each chicken/vegetable serving, being careful not to let it run outside of the foil. Top each serving with a sprig of rosemary if you have it. Fold up foil to make the packet. Fold shorter side up first then close the top by folding the long sides together. Make sure to leave some room in the packet for the steam to cook everything. Crimp tightly to seal well.